mirror of https://github.com/deater/tb1.git
snes: use Y*4 in many cases instead of Y
this in theory trades off lots of shifting for a few increments it does make the code a bit more confusing
This commit is contained in:
Vince Weaver
parent
a6a8904c1c
commit
58178b95cd
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@ -1,2 +1,2 @@
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.word $f93f ; Complement of checksum
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.word $6c0 ; Unsigned 16-bit sum of ROM
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.word $e1c ; Complement of checksum
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.word $f1e3 ; Unsigned 16-bit sum of ROM
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@ -423,22 +423,14 @@ level1_setup_video:
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do_new_game:
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;; set up struct pointers
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; ldx #.LOWORD(missile_0) ; setup missle struct pointer
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; stx MISSILE_PL
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; ldx #.LOWORD(enemy_0) ; setup enemy struct pointer
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; stx ENEMY_PL
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;; Clear BSS
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ldx #$0
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clear_bss:
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stz start_bss,X
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inx
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cpx #end_bss-start_bss
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bne clear_bss
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; ldx #$0
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;clear_bss:
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; stz start_bss,X
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; inx
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; cpx #end_bss-start_bss
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; bne clear_bss
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;; Init one-time vars
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@ -450,7 +442,7 @@ clear_bss:
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; jsr update_shields
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lda #104
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sta shipx ; shipx at start is 18
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sta shipx ; shipx at start is 104
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lda #$1
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sta LEVEL ; start at level 1
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@ -581,13 +573,16 @@ same_enemy_type:
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; find empty enemy slot
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ldy #$20 ; point to enemies[0]
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ldy #$80 ; point to enemies[0] $20 * 4
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find_empty_enemy:
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jsr is_sprite_active
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bcc add_enemy
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iny
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cpy #($20+NUM_ENEMIES)
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iny
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iny
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iny
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cpy #($80+4*NUM_ENEMIES)
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bne find_empty_enemy
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jmp move_enemies ; no empty, slots, move on
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@ -803,17 +798,17 @@ store_enemy_kind:
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; want to store to $200 + (Y*4)
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rep #$20 ; set A to 16-bit
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.a16
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; rep #$20 ; set A to 16-bit
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;.a16
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tya ; copy Y to A
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asl
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asl ; multiply by 4
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tax ; put in X
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tyx ; copy Y to A
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; asl
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; asl ; multiply by 4
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; tax ; put in X
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sep #$20 ; set A back to 8-bit
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.a8
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; sep #$20 ; set A back to 8-bit
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;.a8
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; determine enemy _x
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; if < 0, make random between 2->34
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@ -1809,22 +1804,22 @@ done_with_boss:
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; Missiles are 8,9,10,11 in sprite table
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ldy #$8 ; point to missile[0]
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ldy #$20 ; point to missile[0] (8*4)
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move_missiles:
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jsr is_sprite_active
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bcc loop_move_missiles ; if not active, skip
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phy
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tya
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asl
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asl
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tay
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; phy
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; tya
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; asl
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; asl
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; tay
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lda $0201,Y
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dea
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sta $0201,Y
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ply
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; ply
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cmp #200
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@ -1897,7 +1892,10 @@ done_missile_collision:
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loop_move_missiles:
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iny
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cpy #(8+NUM_MISSILES) ; have we checked all missiles?
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iny
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iny
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iny
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cpy #($20+4*NUM_MISSILES) ; have we checked all missiles?
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bne move_missiles ; if not, loop
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done_move_missiles:
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@ -1948,16 +1946,16 @@ key_A:
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bit #$80
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beq game_unknown
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ldy #$8 ; point to missile[y]
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ldy #$20 ; point to missile[y] (8*4)
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fire_missiles:
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jsr is_sprite_active
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bcs end_fire_loop ; if active, skip to next
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phy
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tya
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asl
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asl
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tay
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; phy
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; tya
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; asl
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; asl
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; tay
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lda #8
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clc
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@ -1968,15 +1966,18 @@ fire_missiles:
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sta $0201,Y
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ply
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; ply
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jsr activate_sprite
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bra done_fire_missiles ; done firing missile
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end_fire_loop:
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iny ; point to next missile
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iny
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iny
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iny
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cpy #(8+NUM_MISSILES) ; see if we have more missiles
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cpy #($20+4*NUM_MISSILES) ; see if we have more missiles
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bne fire_missiles ; if so, loop
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done_fire_missiles:
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@ -272,32 +272,31 @@ found_keypress:
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plp ; restore status
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rts
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;===========================
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;===========================
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; is_sprite_active
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;===========================
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;===========================
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; assumes high sprite table at $0400
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; sets carry if active
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; clears carry if not
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; sprite number in Y
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is_sprite_active:
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php ; save status
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;===========================
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;===========================
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; get_sprite_mask
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;===========================
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;===========================
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; only meant to be called by the routines below
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; sprite number is Y/4
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get_sprite_mask:
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rep #$30 ; A=16bit X/Y=16bit
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.i16
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.a16
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phx ; save X on stack
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phy ; save Y on stack
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tyx ; copy Y to X
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; tyx ; copy Y to X
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; address=$0400 + Y/4
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; address=$0400 + Y/16
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tya ; copy Y to A
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lsr ; divide by 4
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lsr ; divide by 16
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lsr
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tax
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lsr
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lsr
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tay ; copy back to Y
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@ -309,6 +308,26 @@ is_sprite_active:
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.a8
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lda SPRITE_HIGH_LOOKUP,X
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; get bitmask for X
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plx
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rts
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;===========================
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;===========================
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; is_sprite_active
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;===========================
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;===========================
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; assumes high sprite table at $0400
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; sets carry if active
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; clears carry if not
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; sprite number is Y/4
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is_sprite_active:
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php ; save status
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phy ; save Y on stack
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jsr get_sprite_mask
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.a8
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; mask is in A
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and $0400,Y ; sprite on screen when bit is 0
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@ -316,14 +335,12 @@ is_sprite_active:
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sprite_is_not_active:
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ply
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plx
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plp
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clc
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rts
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sprite_is_active:
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ply
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plx
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plp
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sec
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rts
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@ -335,40 +352,20 @@ sprite_is_active:
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;===========================
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;===========================
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; assumes high sprite table at $0400
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; sets carry if active
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; clears carry if not
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; sprite number in Y
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; sprite number is Y/4
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activate_sprite:
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php ; store status
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phx ; store X on stack
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phy ; store Y on stack
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rep #$20 ; make A 16-bit
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.a16
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tyx ; copy Y to X
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; address=$0400 + Y/4
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tya ; copy Y to A
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lsr ; divide by 4
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lsr
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tay ; transfer back to Y
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txa ; get saved copy of Y
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and #$3 ; mask to get low bits
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tax ; transfer back to X
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sep #$20 ; make A 8-bit
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jsr get_sprite_mask
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.a8
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lda SPRITE_HIGH_LOOKUP,X ; load from lookup table
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eor #$ff ; negate it
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and $0400,Y ; sprite on screen when bit is 0
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sta $0400,Y ; store it back out
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ply ; restore values from stack
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plx
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plp
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rts ; return
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@ -379,38 +376,18 @@ activate_sprite:
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;===========================
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;===========================
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; assumes high sprite table at $0400
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; sets carry if active
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; clears carry if not
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; sprite number in Y
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; sprite number is Y/4
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deactivate_sprite:
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php ; save status on stack
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phx ; save X
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phy ; save Y
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tyx ; copy Y to X
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rep #$20 ; set A to 16-bit
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.a16
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; address=$0400 + Y/4
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tya ; copy Y to A
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lsr ; divide by 4
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lsr
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tay ; copy back to Y
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txa ; get low bits into X
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and #$3 ; Mask
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tax
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sep #$20 ; set A to 8-bit
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jsr get_sprite_mask
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.a8
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lda SPRITE_HIGH_LOOKUP,X ; lookup bits in table
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ora $0400,Y ; sprite off screen when bit is 1
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sta $0400,Y ; save value back out
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ply ; restore Y
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plx ; restore X
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plp ; restore status
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rts ; return
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